----- Original Message ----- > From: "Steven Rostedt" <rost...@goodmis.org> > To: "Philippe Proulx" <ppro...@efficios.com> > Cc: "Mathieu Desnoyers" <mathieu.desnoy...@efficios.com>, "Jeremie Galarneau" > <jga...@efficios.com>, "lttng-dev" > <lttng-dev@lists.lttng.org>, linux-trace-de...@vger.kernel.org > Sent: Tuesday, 15 June, 2021 11:57:38 > Subject: Re: [lttng-dev] Usage example of libbabeltrace (babeltrace2) to read > CTF traces from a GUI
> [ Adding linux-trace-devel too ] > > On Tue, 15 Jun 2021 11:13:41 -0400 > Philippe Proulx <ppro...@efficios.com> wrote: > >> I can cook a minimal working example in the following days. > > That would be great, thanks! Here you go (Pastebin: <https://pastebin.com/0MFQkiAw>): - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - #include <stdlib.h> #include <stdio.h> #include <stdint.h> #include <stdbool.h> #include <assert.h> #include <babeltrace2/babeltrace.h> /* * Shared data between our relay sink component and the * bt_graph_run_once() call site. */ struct relay_data { bt_message_array_const msgs; uint64_t msg_count; }; /* * Consumer method of our relay sink component class. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#ga301a677396bd8f5bd8b920fd5fa60418>. */ static bt_graph_simple_sink_component_consume_func_status relay_consume( bt_message_iterator * const msg_iter, void * const user_data) { struct relay_data * const relay_data = (struct relay_data *) user_data; bt_message_iterator_next_status msg_iter_next_status; bt_graph_simple_sink_component_consume_func_status status = BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_OK; /* Consume the next messages, storing them in `*relay_data` */ msg_iter_next_status = bt_message_iterator_next(msg_iter, &relay_data->msgs, &relay_data->msg_count); switch (msg_iter_next_status) { case BT_MESSAGE_ITERATOR_NEXT_STATUS_END: status = BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_END; break; case BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_MEMORY_ERROR: status = BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_MEMORY_ERROR; break; case BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_ERROR: status = BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_ERROR; break; default: assert(status == BT_GRAPH_SIMPLE_SINK_COMPONENT_CONSUME_FUNC_STATUS_OK); break; } return status; } /* * Adds our own sink component named `relay` to the trace processing * graph `graph`. * * On success, `*comp` is the added sink component. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#api-graph-lc-add-ss>. */ static bt_graph_add_component_status add_relay_comp(bt_graph * const graph, struct relay_data * const relay_data, const bt_component_sink ** const comp) { return bt_graph_add_simple_sink_component(graph, "relay", NULL, relay_consume, NULL, relay_data, comp); } /* * Creates and returns the parameters to initialize the `src.ctf.fs` * component with the trace directory `trace_dir`. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-val.html>. */ static bt_value *create_ctf_fs_comp_params(const char * const trace_dir) { bt_value *params; bt_value *inputs = NULL; bt_value_map_insert_entry_status insert_entry_status; bt_value_array_append_element_status append_elem_status; /* Create an empty map value */ params = bt_value_map_create(); if (!params) { goto error; } /* * Insert an empty array value having the key `inputs`. * * `inputs` is a borrowed value object here, _not_ our * reference. */ insert_entry_status = bt_value_map_insert_empty_array_entry(params, "inputs", &inputs); if (insert_entry_status != BT_VALUE_MAP_INSERT_ENTRY_STATUS_OK) { goto error; } /* Append the trace directory to the `inputs` array value */ append_elem_status = bt_value_array_append_string_element(inputs, trace_dir); if (append_elem_status != BT_VALUE_ARRAY_APPEND_ELEMENT_STATUS_OK) { goto error; } goto end; error: BT_VALUE_PUT_REF_AND_RESET(params); end: return params; } /* * Adds a `src.ctf.fs` component named `ctf` to read the trace directory * `trace_dir` to the trace processing graph `graph`. * * See <https://babeltrace.org/docs/v2.0/man7/babeltrace2-source.ctf.fs.7/>. * * On success, `*comp` is the added source component. */ static bt_graph_add_component_status add_ctf_fs_comp(bt_graph * const graph, const char * const trace_dir, const bt_component_source ** const comp) { const bt_plugin *plugin; bt_plugin_find_status plugin_find_status; const bt_component_class_source *comp_cls; bt_value *params = NULL; bt_graph_add_component_status add_comp_status; /* Find the `ctf` plugin */ plugin_find_status = bt_plugin_find("ctf", BT_TRUE, BT_TRUE, BT_TRUE, BT_TRUE, BT_TRUE, &plugin); if (plugin_find_status != BT_PLUGIN_FIND_STATUS_OK) { goto error; } /* Borrow the `fs` source component class within the `ctf` plugin */ comp_cls = bt_plugin_borrow_source_component_class_by_name_const( plugin, "fs"); if (!comp_cls) { goto error; } /* Create the parameters to initialize the source component */ params = create_ctf_fs_comp_params(trace_dir); if (!params) { goto error; } /* Add the source component to the graph */ add_comp_status = bt_graph_add_source_component(graph, comp_cls, "ctf", params, BT_LOGGING_LEVEL_NONE, comp); goto end; error: add_comp_status = BT_GRAPH_ADD_COMPONENT_STATUS_ERROR; end: bt_plugin_put_ref(plugin); bt_value_put_ref(params); return add_comp_status; } /* * Adds a `flt.utils.muxer` component named `muxer` to the trace * processing graph `graph`. * * See <https://babeltrace.org/docs/v2.0/man7/babeltrace2-filter.utils.muxer.7/>. * * On success, `*comp` is the added filter component. */ static bt_graph_add_component_status add_muxer_comp(bt_graph * const graph, const bt_component_filter ** const comp) { const bt_plugin *plugin; bt_plugin_find_status plugin_find_status; const bt_component_class_filter *comp_cls; bt_graph_add_component_status add_comp_status; /* Find the `utils` plugin */ plugin_find_status = bt_plugin_find("utils", BT_TRUE, BT_TRUE, BT_TRUE, BT_TRUE, BT_TRUE, &plugin); if (plugin_find_status != BT_PLUGIN_FIND_STATUS_OK) { goto error; } /* Borrow the `muxer` filter comp. class within the `utils` plugin */ comp_cls = bt_plugin_borrow_filter_component_class_by_name_const( plugin, "muxer"); if (!comp_cls) { goto error; } /* Add the filter component to the graph (no init. parameters) */ add_comp_status = bt_graph_add_filter_component(graph, comp_cls, "muxer", NULL, BT_LOGGING_LEVEL_NONE, comp); goto end; error: add_comp_status = BT_GRAPH_ADD_COMPONENT_STATUS_ERROR; end: bt_plugin_put_ref(plugin); return add_comp_status; } /* * Creates a trace processing graph having this layout: * * +------------+ +-----------------+ +--------------+ * | src.ctf.fs | | flt.utils.muxer | | Our own sink | * | [ctf] | | [muxer] | | [relay] | * | | | | | | * | stream0 @--->@ in0 out @--->@ in | * | stream1 @--->@ in1 | +--------------+ * | stream2 @--->@ in2 | * | stream3 @--->@ in3 | * +------------+ @ in4 | * +-----------------+ * * In the example above, the `src.ctf.fs` component reads a CTF trace * having four data streams. The `trace_dir` parameter is the directory * containing the CTF trace to read. * * Our own relay sink component, of which the consuming method is * relay_consume(), consumes messages from the `flt.utils.muxer` * component, storing them to a structure (`*relay_data`) shared with * the bt_graph_run_once() call site. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html>. */ static bt_graph *create_graph(const char * const trace_dir, struct relay_data * const relay_data) { bt_graph *graph; const bt_component_source *ctf_fs_comp; const bt_component_filter *muxer_comp; const bt_component_sink *relay_comp; bt_graph_add_component_status add_comp_status; bt_graph_connect_ports_status connect_ports_status; uint64_t i; /* Create an empty trace processing graph */ graph = bt_graph_create(0); if (!graph) { goto error; } /* Create and add the three required components to `graph` */ add_comp_status = add_ctf_fs_comp(graph, trace_dir, &ctf_fs_comp); if (add_comp_status != BT_GRAPH_ADD_COMPONENT_STATUS_OK) { goto error; } add_comp_status = add_muxer_comp(graph, &muxer_comp); if (add_comp_status != BT_GRAPH_ADD_COMPONENT_STATUS_OK) { goto error; } add_comp_status = add_relay_comp(graph, relay_data, &relay_comp); if (add_comp_status != BT_GRAPH_ADD_COMPONENT_STATUS_OK) { goto error; } /* * Connect all the output ports of the `ctf` source component to * the input ports of the `muxer` filter component. * * An `flt.utils.muxer` component adds an input port every time * you connect one, making one always available. * * See <https://babeltrace.org/docs/v2.0/man7/babeltrace2-filter.utils.muxer.7/#doc-_input>. */ for (i = 0; i < bt_component_source_get_output_port_count(ctf_fs_comp); i++) { const bt_port_output * const out_port = bt_component_source_borrow_output_port_by_index_const( ctf_fs_comp, i); const bt_port_input * const in_port = bt_component_filter_borrow_input_port_by_index_const( muxer_comp, i); /* Connect ports */ connect_ports_status = bt_graph_connect_ports(graph, out_port, in_port, NULL); if (connect_ports_status != BT_GRAPH_CONNECT_PORTS_STATUS_OK) { goto error; } } /* Connect the `muxer` output port to the `relay` input port */ connect_ports_status = bt_graph_connect_ports(graph, bt_component_filter_borrow_output_port_by_index_const( muxer_comp, 0), bt_component_sink_borrow_input_port_by_index_const( relay_comp, 0), NULL); if (connect_ports_status != BT_GRAPH_CONNECT_PORTS_STATUS_OK) { goto error; } goto end; error: BT_GRAPH_PUT_REF_AND_RESET(graph); end: return graph; } /* * Handles a single message `msg`, printing its name if it's an event * message. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-msg.html>. */ static void handle_msg(const bt_message * const msg) { const bt_event *event; if (bt_message_get_type(msg) != BT_MESSAGE_TYPE_EVENT) { goto end; } event = bt_message_event_borrow_event_const(msg); puts(bt_event_class_get_name(bt_event_borrow_class_const(event))); end: return; } /* * Runs the trace processing graph `graph`, our relay sink component * transferring its consumed messages to `*relay_data`. * * See <https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#api-graph-lc-run>. */ static int run_graph(bt_graph * const graph, struct relay_data * const relay_data) { bt_graph_run_once_status status; while (true) { uint64_t i; /* * bt_graph_run_once() calls the consuming method of * our relay sink component (relay_consume()). * * relay_consume() consumes a batch of messages from the * `flt.utils.muxer` component and stores them in * `*relay_data`. */ status = bt_graph_run_once(graph); assert(status != BT_GRAPH_RUN_ONCE_STATUS_AGAIN); if (status != BT_GRAPH_RUN_ONCE_STATUS_OK) { break; } /* Handle each consumed message */ for (i = 0; i < relay_data->msg_count; i++) { const bt_message * const msg = relay_data->msgs[i]; handle_msg(msg); /* * The message reference `msg` is ours: release * it now. */ bt_message_put_ref(msg); } } return status == BT_GRAPH_RUN_ONCE_STATUS_END ? 0 : -1; } /* * Reads the CTF trace located in the directory `argv[1]`, printing one * event name per line to the standard output. */ int main(const int argc, const char * const * const argv) { int ret = EXIT_SUCCESS; struct relay_data relay_data = { 0 }; bt_graph *graph; assert(argc == 2); /* Create the trace processing graph */ graph = create_graph(argv[1], &relay_data); if (!graph) { ret = EXIT_FAILURE; goto end; } /* Run the graph, printing one event name per line */ if (run_graph(graph, &relay_data)) { ret = EXIT_FAILURE; } end: bt_graph_put_ref(graph); return ret; } - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Build as such: $ cc -Wextra -Wall -o read-ctf-example read-ctf-example.c \ $(pkg-config babeltrace2 --cflags --libs) Feel free to ask us any questions. Philippe Proulx EfficiOS Inc. https://www.efficios.com/ > > -- Steve > >> >> Phil >> >> [1]: https://babeltrace.org/docs/v2.0/libbabeltrace2/ >> [2]: >> https://babeltrace.org/docs/v2.0/libbabeltrace2/group__api-graph.html#gaa8432f03a967d01b764fb1bc959c8e89 >> >> > >> > Thanks, >> > >> > Mathieu >> > >> > -- >> > Mathieu Desnoyers >> > EfficiOS Inc. >> > http://www.efficios.com >> > _______________________________________________ >> > lttng-dev mailing list >> > lttng-dev@lists.lttng.org > > > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
